<template>
    <div style="border:1px solid #ccc;margin:1em;padding:1em">
        Son, {{modelValue}}, {{xxx}}
        <p>
            <button @click="set20">20</button>
        </p>
    </div>
</template>
<script>
export default {
    props: {
        xxx: {type: Number},
        modelValue:{type: Number}
    },
    setup (props, { emit }) {
        const set20 = () => {
            // alert(20)

            // emit('set20')
            // emit('update:modelValue', 20)
            emit('update:xxx', 17)
        }

        return { set20 }
    }
}
</script>